Findings from the current study suggest that the increased talker variability in the PRESTO sentence materials has a detrimental effect on speech recognition in both adult CI users and NH listeners under CI simulation, particularly when speech is further degraded by MTB. For adult CI users, working memory capacity contributes to speech recognition abilities. Sentence recognition testing with high-variability, multi-talker materials, as in PRESTO, provides robust assessment of speech recognition abilities for research and clinical application, generating a wide range of scores for evaluating individual differences without ceiling effects when compared to conventional low-variability sentences.